Implantable medical devices (IMDs), such as implantable pacemakers, cardioverters, defibrillators, or pacemaker-cardioverter-defibrillators, provide therapeutic electrical stimulation to the heart. IMDs may provide pacing to address bradycardia, or pacing or shocks in order to terminate tachyarrhythmia, such as tachycardia or fibrillation. In some cases, the medical device may sense intrinsic depolarizations of the heart, detect arrhythmia based on the intrinsic depolarizations (or absence thereof), and control delivery of electrical stimulation to the heart if arrhythmia is detected based on the intrinsic depolarizations.
IMDs may also provide cardiac resynchronization therapy (CRT), which is a form of pacing. CRT involves the delivery of pacing to the left ventricle, or both the left and right ventricles. The timing and location of the delivery of pacing pulses to the ventricle(s) may be selected to improve the coordination and efficiency of ventricular contraction.
IMDs sense signals and deliver therapeutic stimulation via electrodes. Implantable pacemakers, cardioverters, defibrillators, or pacemaker-cardioverter-defibrillators are typically coupled to one or more subcutaneous electrodes or intracardiac leads that carry electrodes for cardiac sensing and delivery of therapeutic stimulation. The signals sensed via the electrodes may be referred to as a cardiac electrogram (EGM) and may include the depolarizations, repolarizations, and other intrinsic electrical activity of the heart.
Systems for implanting medical devices may include workstations or other equipment in addition to the medical device itself. In some cases, these other pieces of equipment assist the physician or other technician with placing the intracardiac leads at particular locations on the heart. In some cases, the equipment provides information to the physician about the electrical activity of the heart and the location of the intracardiac lead. The equipment may perform similar functions as the medical device, including delivering electrical stimulation to the heart and sensing the depolarizations of the heart. In some cases, the equipment may include equipment for obtaining an electrocardiogram (ECG) via skin electrodes placed on the surface of the patient. In addition, the patient may have a plurality of electrodes on an ECG belt or vest that surrounds the torso of the patient. After the vest has been secured to the torso, a physician can perform a series of tests to evaluate a patient's cardiac response.
During the evaluation process, a physician typically needs to review the onset of cardiac depolarization waves in the rhythms using a computing apparatus. Numerous methods are used to detect onset of depolarization waves. U.S. Pat. No. 8,781,580B2 to Sven-Erik Hedberg et al. is directed to pacing sequence optimization applied through the multipolar LV lead based on a particular optimization criterion which is the time point of the onset of activation of the left ventricle until closure of the mitral valve of the heart. The pacing sequence that minimizes the time interval from onset of LV activation until the mitrel valve closure is identified and used as currently optimal pacing sequence for the IMD. An activation detector is configured to detect onset of activation of the left ventricle for a cardiac cycle. The activation detector is configured to detect onset of contraction of the left ventricle for the cardiac cycle based on i) a signal received by the connector for a connectable sensor or ii) an impedance signal determined by the activity detector based on an electric signal received by the connector from a connectable pacing electrode. Nowhere in this method does it eliminate polarization artifacts to ensure the best channel is selected or adjust detection of the onset of cardiac depolarization to ensure beats are not missed.
Additionally, the Sven-Erik Hedberg method does not address ambiguous cardiac signals. U.S. Pat. No. 7,953,489 B2 to Warren et al. Warren et al does correct for ambiguous signals, defined as sensed cardiac electrical signal that are difficult to comprehend, understand, or classify by an implantable medical device (IMD) (e.g. ICD etc.) system's detection architecture. Warren et al. addresses ambiguous signals by counting to characteristic features, comparing the ambiguous signal to a threshold, and then sensing alternate cardiac signals. This method can be cumbersome since the characteristic features need to be parsed and counted.
It is therefore desirable to develop additional methods and systems for signal processing that allows the system to acquire cardiac signals with little or no artifacts and/or ambiguous signals thereby allowing physicians to more accurately determine therapy for a patient.